Phyllodes tumours (PTs) are rare fibroepithelial neoplasms of the breast, comprising less than 1% of all primary breast neoplasms globally, with a slightly higher incidence in Asian populations and among younger women [1]. These tumours exhibit a biphasic architecture characterized by epithelial-lined clefts embedded in a hyper cellular stromal matrix, often forming a leaf-like growth pattern. Based on histopathological features—such as stromal cellularity, nuclear atypia, mitotic activity, stromal overgrowth, and the nature of tumour margins—the World Health Organization (WHO) classifies PTs into benign, borderline, and malignant subtypes [1,2].

Benign phyllodes tumours constitute the majority, approximately 60%–75% of all PTs, and are typically managed successfully with wide local excision. They demonstrate a low recurrence rate (10%–20%) and extremely low metastatic potential [3,4]. Borderline and malignant PTs, which account for 15%–20% and 10%–20% of cases respectively, are more prone to recurrence and exhibit more aggressive clinical behaviour. Malignant PTs, in particular, are associated with local recurrence rates ranging from 15% to 40%, and distant metastasis occurs almost exclusively in this subgroup, with reported rates ranging from 9% to 27% [3–5]. The lungs are the most common site of distant metastasis, followed by bones, brain, and liver, and the spread typically occurs via the hematogenous route [3,5]. Regional lymphadenopathy may occur; however, true axillary lymph node metastasis remains an extremely rare event, reported only sporadically in literature [6,7].

Although most malignant PTs follow a relatively indolent course post-resection, cases of aggressive progression and rapid dissemination to distant organs have been documented. Chest wall invasion, diaphragmatic extension, and pleural involvement are particularly uncommon and often indicate an advanced and aggressive disease course [6]. Furthermore, the presence of lung and lymph node metastasis at presentation is rare and portends a poor prognosis due to limited responsiveness to conventional chemotherapy.

In this report, we present a rare and aggressive case of malignant phyllodes tumour in a 42-year-old female, who presented with a rapidly enlarging breast mass. Despite undergoing mastectomy and adjuvant chemotherapy, she developed extensive pulmonary metastases, chest wall infiltration, and diaphragmatic involvement. This case highlights the unpredictable nature of malignant phyllodes tumours and underscores the diagnostic and therapeutic challenges associated with such unusual and aggressive metastatic presentations.

A 42-year-old female presented to the surgery outpatient department in November 2023 with complaints of a progressively enlarging lump in her left breast. On clinical examination, a firm, non-tender mass was palpable in the upper outer quadrant of the left breast, without overlying skin changes or nipple discharge. No palpable axillary lymphadenopathy was noted at the time of presentation.

Initial diagnostic workup included mammography and breast ultrasound. Mammography revealed a hyperdense, angular mass lesion, while ultrasonography showed a heteroechoic mass with internal vascularity on Doppler evaluation. Based on imaging characteristics, the lesion was assigned a BI-RADS 4B score, indicating suspicion of malignancy. A core needle biopsy of the lesion was performed, which revealed features consistent with a phyllodes tumour.

Given the rapid increase in tumour size and histological suspicion for malignancy, the patient underwent a left mastectomy with sentinel lymph node biopsy. Gross examination of the mastectomy specimen showed a large, well-circumscribed, lobulated tumour. Histopathological analysis demonstrated stromal overgrowth, marked cellular atypia, increased mitotic activity, and infiltrative tumour margins, consistent with a malignant phyllodes tumour. Sentinel lymph node biopsy was negative for metastatic disease.

The patient subsequently received six cycles of adjuvant chemotherapy and was on regular follow-up. She remained asymptomatic until January 2025, when she developed respiratory complaints including dyspnoea and persistent cough. Chest radiography revealed multiple nodular opacities in both lung fields with associated left-sided chest wall invasion, right costophrenic angle blunting, and obscuration of the right hemidiaphragm (Figure 1). A contrast-enhanced CT (CECT) of the chest was advised for further characterization, which confirmed the presence of multiple pulmonary masses with spiculated margins and surrounding ground-glass opacities, suggestive of angioinvasion (Figure 2). In addition, invasion into the chest wall and extension to the right diaphragmatic crus were noted (Figure 3).

Ultrasound of the thorax revealed a heteroechoic lesion arising from the right diaphragmatic crus (Figure 4). A right-sided pleural effusion was also identified. Pleural fluid aspiration and cytological examination confirmed the presence of malignant cells.

A biopsy from one of the lung lesions confirmed metastatic malignant phyllodes tumour, showing stromal overgrowth and histological features similar to the primary breast tumour. There was no evidence of a primary lung malignancy. Notably, enlarged axillary lymph nodes were also detected and cytologically confirmed to be metastatic—an uncommon finding in phyllodes tumour metastasis.

The patient wasstarted on chemotherapy, but her condition continued to deteriorate. She ultimately succumbed to complications related to advanced metastatic disease. This case highlights a rare presentation of malignant phyllodes tumour with synchronous lung and nodal metastases, along with thoracic extension involving the pleura, diaphragm, and chest wall.

Malignant phyllodes tumours (MPTs) are rare breast neoplasms representing less than 1% of all breast tumours.[8] Although the majority are benign and managed successfully with wide local excision, the malignant variant demonstrates a notable potential for local recurrence and distant metastasis. Koh et al. (2017), in their comprehensive review of 3,516 cases, reported a mean metastatic rate of 20% among malignant PTs, with the lungs, bones, and brain being the most common sites of dissemination [8].

Our patient, a 42-year-old woman, initially underwent left mastectomy for a rapidly enlarging malignant phyllodes tumour. Despite negative sentinel node biopsy and adjuvant chemotherapy, she later developed diffuse lung metastases, chest wall invasion, pleural effusion with malignant cytology, and diaphragmatic extension. This disease progression reflects the aggressive clinical course often seen in high-grade MPTs, with features paralleling those observed by Reinfuss et al. (1996) and Hawkins et al. (1992), who reported distant metastases in 15.9% and 24.2% of cases respectively, and 100% and 87.5% metastatic death rates correspondingly [9,10].

One of the rarest aspects of our case is the confirmed axillary lymph node involvement. While axillary lymphadenopathy may occur due to reactive hyperplasia, true nodal metastasis is highly uncommon in MPTs, which typically spread hematogenously. Koh et al. noted axillary node metastasis in only 1.1% of cases reviewed [8]. Most major series, including Kapiris et al. (2001)[11] and Chen et al. (2005)[12], reported no cases of nodal spread in cohorts of 48 and 172 patients respectively [7]. However, isolated reports, such as those by Agrawal et al. and Sawalhi&Shatti, documented node positivity in individual or small series (14.3% in 42 patients in the latter) [13,14], similar to our finding (Table 1).

The presence of spiculated lung masses with ground-glass halos, as seen in our patient, indicates angio-invasive tumour behaviour, a hallmark of aggressive dissemination. Chest wall and diaphragmatic extension are exceptionally rare and represent late-stage disease. Hawkins et al. observed pleural and musculoskeletal involvement in their high-grade tumours, which correlated with poor prognosis [10].

Histopathological features such as stromal overgrowth, infiltrative margins, high mitotic count, marked atypia, and necrosis—identified in our case—are all strongly associated with distant metastasis, as consistently highlighted across multiple studies. These risk factors were emphasized by Koh et al., along with molecular markers such as Axl, CD10, Six1, and SETD2 mutations as potential contributors to metastatic potential [8].

While wide surgical excision remains the primary mode of management, the efficacy of adjuvant chemotherapy is uncertain. Our patient’s failure to respond to systemic treatment reflects similar outcomes in studies by Reinfuss and Kapiris, where most patients with metastatic disease succumbed within months [9,11]. The lack of effective systemic therapy underscores the importance of risk stratification and surveillance.

Our case represents a highly aggressive and uncommon presentation of malignant phyllodes tumour, with synchronous pulmonary, pleural, diaphragmatic, and nodal metastases. Such presentations are rarely documented in literature. This case highlights the need for awareness of atypical dissemination patterns, the limitations of current treatment modalities, and the importance of exploring molecular targets to guide therapy and improve prognosis.

Table 1: Showing summary of studies with metastatic Phylloidestumor

This case illustrates an exceptionally aggressive presentation of MPT with synchronous pulmonary, pleural, diaphragmatic, chest wall, and axillary lymph node involvement. Comparison with existing literature underscores the rarity of such dissemination patterns. It highlights the need for clinicians to remain vigilant for atypical metastatic routes and advocates for further research into molecular markers and tailored therapeutic approaches.

1. Lakhani SR, Ellis IO, Schnitt SJ, Tan PH, van de Vijver MJ, editors. WHO Classification of Tumours of the Breast. 4th ed. Lyon: International Agency for Research on Cancer; 2012.
2. World Health Organization . Histological typing of breast tumors. Tumori 1982;68:181–98. [DOI] [PubMed] [Google Scholar]
3. Zhang Y, Kleer CG. Phyllodestumor of the breast: histopathologic features, differential diagnosis, and molecular/genetic updates. Arch Pathol Lab Med. 2016;140(7):665–71.
4. Spitaleri G, Toesca A, Botteri E, Bottiglieri L, Rotmensz N, Boselli S, et al. Breast phyllodestumor: a review of literature and a single center retrospective series analysis. Crit Rev OncolHematol. 2013;88(2):427–36.
5. Tan PH, Thike AA, Tan WJ, Thu MM, Busmanis I, Li H, et al. Predicting clinical behaviour of breast phyllodes tumours: a nomogram based on histological criteria and surgical margins. J ClinPathol. 2012;65(1):69–76.
6. Agrawal PP, Mohanta PK, Singh K, Bahadur AK. Cystosarcomaphyllodes with lymph node metastasis. CommunOncol. 2006;3:44–8.
7. Guerrero MA, Ballard BR, Grau AM. Malignant phyllodestumor of the breast: review of the literature and case report of stromal overgrowth. SurgOncol. 2003;12(1):27–37.
8. Koh VCY, Thike AA, Tan PH. Distant metastases in phyllodes tumours of the breast: an overview. Appl Cancer Res. 2017;37:15. https://doi.org/10.1186/s41241-017-0028-6
9. Reinfuss M, Mitus J, Duda K, Stelmach A, Rys J, Smolak K. The treatment and prognosis of patients with phyllodestumor of the breast: an analysis of 170 cases. Cancer. 1996;77(5):910–6.
10. Hawkins RE, Schofield JB, Fisher C, Wiltshaw E, McKinna JA. The clinical and histologic criteria that predict metastases from cystosarcomaphyllodes. Cancer. 1992;69(1):141–7.
11. Kapiris I, Nasiri N, A’Hern R, Healy V, Gui GPH. Outcome and predictive factors of local recurrence and distant metastases following primary surgical treatment of high-grade malignant phyllodes tumours of the breast. Eur J SurgOncol. 2001;27(8):723–30.
12. Chen WH, Cheng SP, Tzen CY, Yang TL, Jeng KS, Liu CL. Surgical treatment of phyllodestumors of the breast: retrospective review of 172 cases. J SurgOncol. 2005;91(3):185–94.
13. Agrawal PP, Mohanta PK, Singh K, Bahadur AK. Cystosarcomaphyllodes with lymph node metastasis. CommunOncol. 2006;3:44–8.
14. Sawalhi S, Al-Shatti M. Phyllodestumor of the breast: a retrospective study of the impact of histopathological factors in local recurrence and distant metastasis. Ann Saudi Med. 2013;33(2):162–8.